1. Field of the Invention
The present invention relates to an ink cartridge and a liquid ink feeder for storing liquid ink for use with an ink jet printer or another printer and feeding the ink to the printer.
2. Description of Related Art
A conventional method of feeding liquid ink to an ink jet printer or another printer includes storing liquid ink in an ink tank made of resin, and mounting the tank on the print head of the printer. The amount of the ink remaining in the tank can be determined by the transmittance of a light illuminated through the tank. Otherwise, the remaining ink amount can be determined by the electrostatic capacity between two electrodes fitted in the tank.
These methods necessitate making an ink tank suitable for a particular mechanism for detecting the remaining ink amount. As a result, the ink feeder is complex in structure. In addition, because the tank is not compatible among types of machines, the tank production costs are high.
FIG. 1 of the accompanying drawings shows part of a conventional liquid ink feeder 12 for an ink jet printer. The feeder 12 includes a tubular needle 16. Liquid ink is stored in an ink cartridge 10 in bag form made of synthetic resin film. The needle 16 can pierce the bottom 11 of the cartridge 10 and protrude into the cartridge. The ink can then be fed from the cartridge 10 through the needle 16 to the print head (not shown) of an ink jet printer.
As shown in FIG. 7 of the drawings, the cartridge 10 is made of multilayer film 303 including an inner synthetic resin film 300 and an outer synthetic resin film 302, which are laminated together. The inner film 300 is a good barrier, and may be a biaxial oriented film of polyethylene (OPP), a biaxial oriented film of high density polyethylene (HDPE), a uniaxial oriented film of high density polyethylene, or the like. The outer film 302 is high in mechanical strength, and may be a uniaxial or biaxial oriented film of nylon, polyester or the like, which is strong mechanically.
When the needle 16 pierces the multilayer film 303, as shown in FIG. 7, cracks 300a are liable to develop in certain directions in the outer layer 302 under the influence of the crystal orientation due to the drawing. The cracks 300a propagate to the inner layer 300. Air may enter the cartridge 10 through the cracks, and mix with the ink in the cartridge. The mixture may cause defective operation of the print head of the printer. Ink may leak through the cracks.
The inner layer 300 may be OPP, HDPE or other synthetic resin film which both functions as a barrier and has mechanical strength. In this case as well, cracks are liable to develop in certain directions.
Particularly, if the feeder 12 is used with a hand-held or portable ink jet printer as disclosed in Japanese Patent application Laid-Open Publications No. 8-295096, No. 8-298568, No. 9-;85994 and U.S. Pat. No. 5,634,730, the ink in the cartridge 10 expands with the operator's vital warmth. As a result, a large amount of liquid ink may leak through the cracks and through the pierced hole of the cartridge 10 around the needle 16. The operator's hands, recording paper, etc. may be smeared with ink. The leaked ink may break the electrical equipment in the printer.
In order to find the amount of the ink remaining in the cartridge 10, it is necessary to detect the level of the remaining ink. This necessitates fitting a plurality of optical or light sensors at predetermined longitudinal intervals, thereby increasing the production costs.